Black print on tracing cloth and method of making same



Patented May 10, 1932 UNITED STATES PATENT- OFFICE KNUID MURCK, OI FOREST HILLS, NEW YORK, ASSIGNOR TO CHARLES BRUNIN G COM- PANY, IN C., A CORPORATION OF NEW YORK BLACK PRINT ON TRACING CLOTH ANID METHOD OF MAKING SAME No Drawing.

This invention is concerned with the reproduction of illustrations, drawings and tracings on ordinary commercial tracing cloth.

' Such reproductions on tracing cloth from tracings are made by first preparing the tracing cloth, then making a negative from ,ihe illustration to bevreproduced and thereafter making a print from the negative on the prepared tracing cloth and then develop ing the latter.

As a result of this process there is obtained a print on tracing cloth of black lines on a very light background, and it may be called a tracing cloth positive.

In carrying out this known process, the tracing cloth is necessarily waterproofed and the print is made on top of the waterproofing and heretofore there has been no known means, so far as I know, for removing the waterproofing from the tracing cloth. The resulting tracing cloth positive print has therefore not been altogether satisfactory.

The fact that the waterproofing remains on the finished print is a serious objection and obstacle to the commercial utilization of this method on a large scale, because the waterproofing makes the print more opaque than ordinary tracing cloth and quite brittle. The black lines are easily washed 011' or peel or run when water happens to be spilled on the print. The latter also turns yellow after a comparatively short time and the appearance ofthe print is not good. I

have discovered a means for removing the waterproofing from a tracing cloth.pos i-. tive print, so that I am able to make and finish such a prmt in a manner that it looks exactly like an original tracing, has the same charac- 'zeristics and in which the tracing cloth pernits of the same treatment by a draftsman as nay be made on or with an original tracing :uch as erasures, the use of drawing ink for naking corrections, the applications of color, :uperior transparency for blue printing purnoses and the like. In order to accomplish Application filed May 31, 1930. Serial No. 458,893.

this result, the tracingcloth is brought back to its original condition, and this has not heretofore been possible so far as I know. In fact, a tracing cloth positive print made according to the herein described method is almost superror in appearance to that of the original tracing. The two can hardly be told apart.

For the purposes of explaining this invention, use is made 'of the words tracing, tracmg cloth and other Well known names of materials. However, these and other terms,

words and names are used in a purely illustrative sense only and not as limiting the inyention. The process comprises the followmg steps.

Firstz-The tracing cloth is Waterproofed by coatmg it with a suitable water proofing solution and thereafter it is dried. An eighty gallon water proofing solution may be made by mixing the following ingredients.

Dibutyl phthallate 17 lbs. Butyl propionate 14 lbs. Lacquer 50 gallons Acetone -l 59 gallons Dibutyl phthallate may be replaced wholly or in diethyl phthallates, tricresyl or-j'triphenyl phosphates, dibutyl or diethyl tartrates, triagetin or other plasticizers or mixtures there- 0 Butyl propionate may bereplaced wholly or in part by suitable quantities of ethyl lactate, diacetone alcohol, tetrachlorethane, furfural or other high boiling solvents or mixtures thereof. w

Lacquer in the a e formula is an acetone solution of a low" ,1 cosityrnitrocotton, the viscosity of the solution 117-125 by theMacMichael viscosimeter'i" It may be replaced by cellulose acetate.

Acetone may be replaced wholly or in part by suitable quantities of ethyl, methyl, amyl or butyl acetates, amyl, butyl orisoprophyl part by suitable quantities of diamyl or quantity of ammonia and sufficient water for one liter with 110 grams Le Pages glue 12 grams Potassium bichromate Silver nitrate"; 90 grams Potassium chloride grams Alcohol, formula 30'. 360 c. c. Concentrated ammonia Variable small Y quantity Water to make 1 liter Alcohol, formula 30, is a specially denatured alcohol made by adding 10 volumes of pure methyl alcohol to 100 volumes of ethyl alcohol.

, Third :-In making a print on the waterproofed and coated tracing cloth it isnecessary to have a negative of an original which is made photographically or by any other means on suitable negative material such as cloth, paper, glass, film or the like. Such a negative has of course white lines on an opaque background. The negative is placed against the coated side of the tracing cloth, exposed to light and a print made in the usual manner of making prints from a negative.

Fourth :The printed cloth is then washed with water to remove the emulsion from the unexposed portions thereof. That is to say,

the emulsion which was under the opaque portions of the negative is removed with water.

Fifth :-Thereafter the print is developed by being placedin a developing bath which may consist of Sodium carbonate (soda ash) 4 oz. Sodium sulphite 4 oz. Hydroquinone oz.

Monomethylparaminophenolsulphate oz.

The latter chemical is sold under a variety of trade names such as metol, pictol, rhodol,.

etol and others.

In the developing bath the exposed portions or. lines on the print turn black, while the background is practically white or very light in color.

Sixth :After having been developed, the print is again given a water bath or washed to remove all surplus developer and then -dried..

. Seventh :-The last step in the process consists in dipping the finished print into a solution adapted to remove the waterproofing from the tracing cloth without removing the printed lines.- One gallon solution for waterproof removing may be made according to the following formula:

Methanol 1 volume Ethyl lactate 1% volumes Alcohol, formula 30 10 volumes or Butyl propionate 7 fluid .oz. Acetone L 9 fluid oz. Alcohol, formula 30 1 fluid oz. Butyl alcohol 35 fluid oz. Carbon tetrachloride 63 fluid o'z. I prefer, however, to use the first of these waterproofing removing formulae.

The print is left in the last named solution for a certain time determined by experimenting. Care must be. taken not to leave .the print in the solution too long, because the printed lines are on top of the waterproofing so to speak and if the print is left in the solution too long, theprinted lines will also be removed.

Eighth :-Thereafter the print is dried by placing it face downward on a sheet of blotting paper and dried by applying a rubber:

squeegee. This removes the waterproof solution from the print, the face of which is dried being next to the blotting paper. It also appears, that the printed lines on the tracing are practically squeezed into the chanically. I

The finished print is not waterproof any longer and the tracing cloth regains -1ts natural appearance and characteristics. It is a black line positive print on tracing cloth having a superior appearance and all the characteristics of an ordinary tracing on tracing cloth.

I claim g .1. The method of producing prints on tracing cloth which consists in waterproof ing the cloth, coating it with a light SGIlSlt-lVt coating, exposing the tracing cloth with negative to produce a print, developing thl printed tracing cloth and thereafter remov ing the waterproofing.

2. The method of reproducing an origina tracing on tracing cloth which consists i: waterproofing the cloth; coatingit withlight sensitive coating capable of being re moved by washing, after ex osure, from th unexposed portions thereo exposing sai cloth with a negative of the original to pr duce a developable print; washing the priI to remove surplus coatin developing th print and washing the print to remove tic waterproofing from the non-exposed portioi thereof.

Signed at New York city, in the count of New York and State of New Yorf May, A. D. 1930.

' KNUD MURCK.

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